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  #1441  
Old 10-03-2013
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by Brent Swain View Post
That is why a 30 calibre bullet which can go thru 23 inches of douglas fir , can barely make it thru 3/8th inch mild steel plate. That is a test of impact resistance. That is why you can tie a knot in steel wire or steel rod without breaking it. Doesn't work so well with wood or fibreglass.That is what would have saved the Sleavins, had they been in a steel boat. That was a single hit impact, as was the impact on the Gringo.
Steel simply stretches and deforms, without leaking, where other materials would shatter.

Several of my boats have put in radiused chines, including my own, only an extra weeks work ,max. It's not a lot of extra work ,far less than building a radiused chine boat using traditional methods. For one thing, you only have 14 feet per side of radius to put in on a 36, far less than a full length radius on traditionally built boats. I have suggested that owners finish the rest of the steel work first, then decide if they consider it worth the effort. Few have . Most want to get out sailing.

When you have corrosion problems on a steel boat you are doing something wrong. Usually it is steel which was not clean enough in the first place or paint too thin. My steel came wheel abraded ( shot blasted) and primed with cold galvanizing primer right from the supplier. It had zero mill scale. After finishing the steel work, I washed the primer, first with TSP to get rid of any grease, then with vinegar to get rid of any oxide on the zinc, then with water. I let it dry for an hour or so in the hot of August sun, then gave her three coats of epoxy tar inside, and five outside, followed by marine enamel outside. That was 29 years ago. a couple of years ago I ground some of the few rust spots in the bilge, and gave her a couple of more coats of epoxy. Outside, I give her decks a coat of enamel every couple of years and her hull a coat of enamel every few years. After 29 years of mostly full time cruising, the steel is 99% as good as the day I built her.
Unlike boats made of other materials, cleats don't work lose, and welded down deck gear and fittings never leak. In any kind of weather , she is as dry inside as a boat can be.
Brent, instead of cross-checking the above against your other posts in the BSMP - how about we just focus on the Ballpeen Fifteen? I'm thinking you could get a lot out of being part of it.
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  #1442  
Old 10-03-2013
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Re: Pros and cons of steel sailboats

Brent:
Yep, I think it will be a bit tippy but I have rowed shells and wherries and I know tippy. I think there may be more flare to the topsides than it appears in that view.
I have been struggling with the seat height. But considering your experience I'll keep it low. Right now it's 10" high off the bottom of the skiff. What do you think? Too high?

Jeff:
It's odd but when you develop a hull like this you don't really have what you and I call a lines drawing. But I can make one. Give me some time to sort out the actual shape then I'll chop it up into the conventiional views.

I'll think about your side deck suggestion. I'm loathe to make changes that would add weight.

Smackenheimer:
I changed the name to the PERRY PEENER PEAPOD.
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  #1443  
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by bobperry View Post
Oh yeah, I guess I should warn you:
This is not a simple Brent style one seam cut origami hull. This is "advanced origami" with three longitudinal cuts per side and two vertical cuts per side. The longl. cuts are quite a bit longer than Brent's. They go to just short of the ends. I just can't get enough control of the shape with one cut. It's more welding work but more control. I am determined not to let the method dictate the shape. But I have it "smashed out", i.e. unfolded so it can all be cut from one flat sheet per side. It looks really strange flattened out.

I could post the smashed version but I'm not sure I want to give away all my treasure yet. I'd hate to have someone run off and start cutting while we are still playng with the basic design.
I keep picturing it 61' long with a deep bulb keel and cast off racers carbon rig.
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Re: Pros and cons of steel sailboats

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Originally Posted by bobperry View Post
Smackenheimer:
I changed the name to the PERRY PEENER PEAPOD.
How about the Perry Peenpod?
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Re: Pros and cons of steel sailboats

When you have it developed to your satisfaction, please post the flat pattern - I'd find it interesting to see what a shape like that would look like before folding it up.
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Re: Pros and cons of steel sailboats

After thinking about what a beautiful dinghy others were describing I realized that mine were as sophisticated as a 4x8 john boat made out of two sheets of plywood.
Aluminum angle in a square around the transom, channel up the center to the bow, and more angle down both sides from the bow back to the top corners of the transom. aluminum plates cut and welded in to complete the hull. I am sure that Brent could greatly improve on my simplicity.
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  #1447  
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Re: Pros and cons of steel sailboats

Let's see if we can work though some of your points one at a time and come to some kind of agreement:

Quote:
Originally Posted by Brent Swain View Post
Steel weighs around 495 pounds per cubic ft, Douglas fir around 35 lbs per cubic foot. Steel has a tensile and compression strength of 60,000 PSI , fir around 1500

The 3/16th steel plate I use on my boats has 2.5 times the weight of 1 inch fir and 7.5 times the tensile strength, giving steel a tensile and compression strength to weight ratio three times that of douglas fir. That is why big ships are no longer made of wood .
When engineers talk about the strength or stiffness of a hull skin material, tensile strength and compression strength are only a small part of the equation. From an engineering standpoint, there are a couple formulas that quantify the strength or stiffness of a hull skin material. For bending the formula is Fb (allowable stress in bending) times S (section modulus) and for stiffness it is E (modulus of elasticity) times I (moment of inertia). The formula for 'S' for a rectangular shape like plating is [B (width of the section) times D squared] divided by 6. The formula for 'I' for a rectangular shape like plating is [B (width of the section) times D (depth of the section) cubed] divided by 12. (I will be showing formulas and results below. Please feel free to check my calculations and assumptions)

So, for comparison 3/16" plating weighs 7.73 lbs per square feet. The same weight per square foot fir would be 2.65" thick. But to produce a fir hull skin with optimized performance in bending, sheer, and impact, the hull would be laminated and would ideally have a kevlar/vinylester sheathing material. Allowing for adhesives and the sheathing, fir hull that weighed the same as 3/16" steel plate would be closer to 2 1/4" thick in thickness.

The section modulus for a 1 foot wide piece of 3/16" steel plate is 0.0703125
inches cubed. The section modulus for a 1 foot wide piece of 2 1/4" thick Fir (ignoring the structural properties of the sheathing) is 10.125 inches cubed. The moment of inertia for a one foot wide piece of 3/16" steel plate is 0.0066 inches to the fourth. The moment of inertia for a 1 foot wide piece of 2 1/4" thick Fir (ignoring the structural properties of the sheathing) is 11.3906 inches cubed.

The allowable bending stress for A-65 steel is 39 KSI (KSI means 1,000 lbs per square inch and 39 KSI is a very big number). Fb for douglas fir is only in the 1.35 KSI range. Similarly, the E (modulus of elasticity) for steel is 30,000 KSI, while the E for Douglas fir is only 1,400 KSI. Looking at these Fb and E numbers it is easy to think that steel has to be stronger.

But when you multiply out S x Fb the two materials, the S x Fb for the 3/16" steel plate comes out to 2,742 Lb.in. while the S x Fb for the 2 1/4" thick Fir comes out to 13,669 Lb.in., which means that the same weight Douglas Fir panel is actually 5 times stronger in bending.

Similarly, when you multiply out E x I for the two materials, the E x I for the 3/16" steel plate comes out to 198 K.sq.in., while the E x I for the 2 1/4" thick Fir comes out to 15,947 K. sq.in., which means that the same weight Douglas Fir panel is actually 80 times stiffer.






Quote:
Originally Posted by Brent Swain View Post
However, where steel really comes out ahead is toughness, the ability absorb impacts by stretching , instead of shattering on the first impact. That is why a 30 calibre bullet which can go thru 23 inches of douglas fir , can barely make it thru 3/8th inch mild steel plate. That is a test of impact resistance.
There is no doubt that steel is a tough material. You are also right that 2 1/4" douglas fir, in and of itself, will not do much to stop a bullet or offer much abrasion resistance.

But if for some reason, you really want your boat to stop a bullet, then the vinylester/kevlar sheathing on the fir hull will result in a much greater stopping power than a steel hull, which is why the military has switched almost exclusively to using kevlar for helmets, armor and skid pads on thier vehicles and aircraft, and is the reason that Kevlar/vinylester is considered the safest material for motorcycle helmets.

Kevlar used to be wildly expensive and hard to use, but it has come down in price enormously and between prepregging, and vaccuum bagging is actually a pretty easy material to use in this kind of application.

Now then, if the guiding criteria is being able to abraid against coral or a rock for long periods of time, then steel probably is the right choice. But if the goal is to produce a lighter and stronger boat which can withstand an impact with a shipping container, or other sharp immovable object, and to survive a hard grounding on a rocky shore for a reasonable period of time, then I suggest that the laminated fir with vinylester/kevlar sheathing may be a better way to go.

Quote:
Originally Posted by Brent Swain View Post
Water flowing across a chine, does so at a very shallow angle. As water across a chine runs at a very shallow angle to the chine, it doesn't take much of a radius to eliminate any resulting turbulence there.
That basically agrees with my point on the comparatively flat angle chines seen on some origami designs. Where we may need to agree to disagree is on the statement, "it doesn't take much of a radius to eliminate any resulting turbulence there."

If I had to rephrase that to be something that I could agree with, I would say something like, "it is unlikely to eliminate turbulence at the chines without fairing the hull transversely, but turbulance at the chine can be reduced to a point where it is effectively inconsequential on a heavy displacement cruising boat."


Quote:
Originally Posted by Brent Swain View Post
Unlike boats made of other materials, cleats don't work lose, and welded down deck gear and fittings never leak. In any kind of weather , she is as dry inside as a boat can be.
Here is where you and I do not agree. Properly installed hardware on fiberglass or properly built wooden boats does not 'work itself loose'. Its easy to reach that conclusion looking a production coastal cruisers, where there rarely are backing plates, potted fastening holes and lock bolts. And yes those steps require extra labor, but done properly fittings do not loosen up on their own.

On the other hand, I think you are right that no matter how good a job one does bedding fittings on these other materials, sooner or later they will leak and sooner or later they will need rebedding.

Quote:
Originally Posted by Brent Swain View Post
When you build a fibreglass or wooden hull and deck, you still have to go out and acquire cleats, mooring bitts, chain plates, hatches, hatch hinges, lifelines, bow roller, install engine mounts, tankage, anchor winch , heater, self steering, inside steering, etc., etc. , all of which is done, at a much lower cost, when you have finished all the metal work on a steel boat, making finished steel work a much bigger part of the total cost of the boat , compared to boat building in other materials
To me, this one seems just plain bogus. If an owner is considering whether to build a steel boat or a fir/composite boat, there is no reason that owner cannot chose to make his hardware in virtually the same manner on each. If that owner was going to fabricate his cleats, mooring bitts, chain plates, hatches, hatch hinges, lifelines, bow roller, engine mounts, tankage, anchor winches, heaters, self steering, etc from scrap steel or scrap stainless, there is no reason that same owner cannot fabricate everyone of those parts for his fir/composite boat, for virtually the same price.

Respectfully,
Jeff
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Last edited by Jeff_H; 10-03-2013 at 07:30 PM.
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by Jeff_H View Post
To me, this one seems just plain bogus. If an owner is considering whether to build a steel boat or a fir/composite boat, there is no reason that owner cannot chose to make his hardware in virtually the same manner on each. If that owner was going to fabricate his cleats, mooring bitts, chain plates, hatches, hatch hinges, lifelines, bow roller, engine mounts, tankage, anchor winches, heaters, self steering, etc from scrap steel or scrap stainless, there is no reason that same owner cannot fabricate everyone of those parts for his fir/composite boat, for virtually the same price.

Respectfully,
Jeff
Totally - that was (is?) one of Bruce Roberts biggies. He provided sheets of drawings of that stuff for construction by the builder - I remember he offered some designs for making a wheel steering system out of a truck differential.
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  #1449  
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Re: Pros and cons of steel sailboats

OK, I'll give you a peak at the preliminary work.
Desert Rat was the inspiration for this. Good thinking Rat.

So:
This is not the boat.
This is almost close.
This is MY INTELLECTUAL property.
But since you have been involved all the way since the dream of this boat started with the Rat's post I will show you.

This is preliminary and obsolete as per my talk with my 3D guy tonight. We will make this perfect. Just give me a few days.

Enjoy.
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Last edited by bobperry; 10-03-2013 at 08:32 PM.
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Re: Pros and cons of steel sailboats

I show you guys some real stuff and you are silent.

I understand. It is amazing and you can't think of anything to say.

It is the creative process.

Enjoy it. Have fun with it. Just oogle and ahhh with it. That's enough.
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